Wide-range variabde frequency generator



June 17, 1947. v. D. LANDON 2,422,424

WIDE RANGE VARIABLE FREQUENCY GENERATOR Filed April 19, 1944 Lanode electrode.

IVWrrJiifimNciuWeinmannEFREQUENCY' GENERATOR ,Vernon D; K'Landon, Princetom N. J V"assigner to RadiolCorporationofAmerica,iacorporation'of* Delaware s ,Application April r19, 1944,- SerialfNof. 532,017

IIlfiisinventionrelatesgenerally-tto oscillation y generators andffmore particularly. to WideY range variable frequency. oscillation Agenerators .employing suitably `connected variable reactance tubes asithe adjustable reactance elements 'of an oscill.

vlatory circuit.

Naria'blereactance .tubes`have been employed extensively.. Vheretofore as, automatic -frequency vcontrol devices .for .controlling the `frequency of .local oscillators-in conventional superheterodyne radio vreceivers .to ,providestabilization of the re- .Gower/,intermediate frequency, in l[the Apresence vof varyingisignal.frequencies orslight variations in .the-receiver -circuitftuning components.

.It,is IWell knownthatlthe '.-anode circuit impedance of a` conventional ,thermionic discharge' tube maylbermade reactive bygapplyinga voltage to .thetube control felectrodewhich is substantially Ainouadrature .withthe .voltage applied to thetube `If ,the rvoltage .applied ,".to the ,tube `control .electrode leads y.the voltage. applied ,to.the.-.anode electrode, theanode-.cathode-impedance -.of. the .tube appears to tbe a ,capacitive re- .actance Similarlyif the .voltage appliedto-the control electrode lags .behindithe voltage applied to ;the anode, the anode-cathode v.impedance .of the tube -appearssto .be .an .inductive l. reaotance. The power ,factor .of the effectively reactive vrietwork represented by the. anode-cathode circuit of the tube-iszero if Vthe controlelectrodeandanode -maltages/:are exactly .in quadrature, The effective power :factorwis apositive value :if .the .control electrode yand anode 4voltages .have a relative .phase -angle .of .lessfthan 90 .and .the effective `power.factor `may assume .anegatVe value the .relative phase-angle of the control .electrode-and anoder-voltages fismore .than.90v.

Infaccordancewith .the instant invention, an oscillation generator. .is provided. by shunt-con- .n.ectingztworeactance tube-circuits, oneof which .provides anfeffeotivecapaeitivefreactanceand.the .ot-baeroiy 'which' provides Yan effective .inductive .rear-:tancey and wherein Ythefnet effective `power factor, koit the `shunt-rconnected reactance tube circuits :is ,a negative value. The,oscillation;fre quency therefore Will depend l-upon I.the parallel resonancewof the effectiveA ,ractances yprovided by the reactan-ce tube:circuits- This-.frequency may be. adj-usted readily. by A.control-ling either one` or bothV of `tloeibias 'voltages applied/cto .the- .control electrorleecathode circuits vrof fthe-reactanee tubes. desired, asingle bias. volta-gepmay .be applied to .the .circuity to vary; the .effective inductive and capacitive.reaetancestherein inthe sameor opposite senses.

The -resultantrcircuit thereby provides a .variable .requency oscillator generator wherein .the

.quency adjustment is providedfby meansV of ad:` justable. bias voltages applied `to one orfboth of vthe. shunt-connected lreactance tubes.

Amongthe objects ofthe'invention aregto` provide.. an improved methodofandmeansjfor generating s. oscillatory currents. Another object .of theinvention is'to provide anfimproved method of and means 4for generating j and controlling the frequency of.. oscillatory currents.v A furtherobjectA of .theinvention `is Vto ,provide an improved method ofV and means for, generating oscillatory currents and. controlling the frequency of said generated .s currents by, means of 1 a unidirectional control-voltage. Anadditional obiectof theinvleritionis toprovide an improved adjustableirequency oscillatonsgenerator wherein thegenerated "frequency mayv be` adjusted continuously over a .relatively Avvide [frequency range. Y

/Otherobjects oithejnvention include improved methodsof. and means fior. employing combina? tions ofz inductive vand capacitive ,therrnioniov dis.- 4charge .reaotance tube Lcircuits.. for the genera.- tion of oscillatory-currents Anadditional object ofltheinventionis to provide-means for varying simultaneously .or selectively .theefiective react,- ,ances of saidgreaetanceeLtube ,circuits to control .continuously .the frequency of said. oscillatory currents. .Another obiectof the, invention is to provide anl irriproved` rnetl'iod ofeand Ymeans l,for -generatingoscillatorycurrentsofpredetermined Wavejiorm and applying .said generatedrcurrents .toaiload device.. i

The invention :will ..be .descrihedllin iurther.-y 'detail'fby .reference .tothe accompanying .drawing of WhichFi'gures 1 to inclusive, are schematic .circuit diagrams of .typical thermionic discharge :reactance 4.tube circuits of .types l known .in lthe prior. art,l Figure` 7 ,is ,aschematic circuit diagram of apreierred embodimentv of Ethe .invention in,- .clu'd'ing in .-.combination ,the i. reactance v.tuber'sircuits oi'JEigures Zand. 6, and' Figure' 8 is ,a .schem- '.atic' .circuit diagram. Aoi" ra modification. of said ,preferred embodiment ,of theinvention l Referring r.to,1-.igure 11j, a typical-inductivereactancertube networkof.atyperemployed extensively in the prior art `includes a triode .thermionic ,discharge .tube ,if havingits anode electrode .connected vvto afirst output` terminal .3. and Vits f cath- -ode 'connected f vto ,.a second output terminal. 15 which may-be grounded. `The .positive yterminal Vof..a source ,of anode-potential, not shown, ,is ap- ,plied tothe anode of. Vthe,.tub.e I- .th-roughan anode resistor 1. 'The negative terminalofjthe anode .voltage source is connected to .the tube cathode,. A reactive network comprisinganin- ,duotor A, a Aresistor B and a capacitorjC, serially- .connectedinltheorder named, is. connected between .the .anode and; cathode electrodes of `vthe tube. .L AA; `coupling capacitor Dfis, connectedlbetween tle'.commongterminals or "the iinductor 'A and resistor B and the control electrode of the thermionic tube I. Thenegative terminal of a source of grid bias potential, not shown, is con- 'nected through a grid resistor E to the control electrode of the tube I. The positive terminalof the grid bias voltage source is connected to grounded cathode.

The reactive network comprising the serially-v, connected inductor A, resistor B and capacitor C comprises a phase splitting network whereby alternating voltages which may be applied to the terminals 3, 5, and hence to the anode and control electrodes of the thermionic tube I are substantially in phase quadrature, the control electrode voltage being lagging. The eective yin lpedance across the output terminals 3, .5 thereforev ,representsVv an effective inductive reactance. YThe effective valueof the inductive reactance appearing at the output terminals 3, .may be'controlled over a relatively wide range by ladjustment 'of the negative biasing voltage appliedthrough the grid resistor E to the control electrode-cathode` circuit of the tube.

' Figure 2 is similarfto the circuit of Figure 1 .withthefexceptionthat the phasesplitting reactive network,connectedbetween the anode and cathode electrodes of the tube I includes a capacitor A, vagresistor .B and an inductor C, se-

the

rially-'connected in the orderV named, and wherein theV controlelectrode ofthe tube I is coupled throghthe coupling capacitor D tothe Vcommon terminals of the capacitorA and the resistor B. v,The eiiectiveimpedance provided across the output terminals 3, 5 ,therefore represents an eiecl tive capacitive reactance since the voltages appliedjjto thejtube4 control electrode substantially leadljthe voltagesapplied tojthetube anode by a phase' k'angle ofthe vorder of 90.

Q The circuit of Figure' is substantially iden- ,tical to thecircuit ofQFigurey 1 with the exception that the control electrode `of thethermionic tube I is,con`nected through theVV coupling capacitor D ,t'othexcominojn terminals of the resistor A and capacitor Bof the serially-connected phase splittingnetworkrC, A, B. VSince'the voltage applied n tothe tube control electrode lags the voltage ap-Y plied to the anode by a phase angle ofv the order AoffiO", the impedance across the output terminals 3,'5 eiectively comprises an inductive reactance. .e

The circuit 01 ,Figure 4 is similarto the circuit ofl FigureZ with the exception that the control electrode of the thermionic tube ".I is connected throughthe coupling capacitor D to the common terminals ofthe resistor A and inductor B of the serially-conneoted phase'splittingnetwork C, A, B. vSince thevoltage applied tothe tube control electrode leads. lthe voltage applied to the anode Vby, a phase angle of the orderl of 90, the impedance/ across the output terminals 3, 5 comprises an effective capacitive reactance. l v .Y In the circuits of F'iguresl 1 tov4, inclusive, if 'the,circuitelement C isY omitted, or has a substanjtially zero impedance, if the coupling capacitor D isa relatively, largecapacitance and if the grid resistor E is a relatively high resistance, the controll'electrade voltage willhave a phase angle lslightlyjless than',90\ `with respect to the anode lpotentialwhen anJalternating potential is ap'- 4 of the element A should exceed orbe of the order of ten times the impedance of the element B of the phase splitting network over the desired frel quenCy range.

- trated in the circuits of Figures 5 and 6. In the circuit of Figure 5, the phase 'splitting network connected-between the anode and cathode tube electrodes comprises a resistor A and capacitor `B serially connected between said electrodes in Vthe -order named. The capacitor B is shunted by a series reactive circuit including a second capacitor 1, a second resistor 9 anda third capacitor/II V.The common terminalsof the `second resistor 9 vand the thirdcapacitor I'I are'connected tothe control electrode of the tube I. y `As in the circuits illustrated by Figuresl tov 4,

the effective impedance of the circuit element-*A should beat least ofl theorde'r of ten times the Vimpedance of the circuit elementB, thereby prov iding nearly phase shiftubetweenvthe tube lanode, voltage and thefvoltage on thejcommon terminal of thev elements Aand B throughout the desired frequency range.rv The second resistor!) should have considerably lessV impedancev than the thirdYcapacitorII'v whereby the circuit elements 9, I I result in aslight additional phase' shift which preferablyfisr sucientto increase the relative phase'angleof the voltages applied to anode and control electrode to slightly in excess of 90. I t should be understood that the second capacitor V'I comprises a relatively large blocking capacitorfor thepurpose of isolating the control electrode of the `tube I from the anode. biasing potential. Asl inthe circuit illustrated by Figure 3, the voltage applied to the control electrode lags behind the voltage 'appliedfto the anode of the tube I, thereby providing an output impedance, across the output terminals 3, 5 which isl eiectively an inductive reactance. n

The circuit of Figure 6 is similar to the circuit of Figure 2 .with the exceptions that the inductive reactor, C ishomittedand 'the relative irnpedances' of the circuitelements A with respect to` B'and of D with respect to E shouldbe pro-y second resistivefelerne'nt E throughout thedesired frequency range. VThe effective input impedance across theoutput terminals V3, 5 therefore effectively comprises` a capacitivereactance with`a negative power factor; f f e' TheV circuit Yof Figure?, which comprises a pre-- ferred embodiment of the instant invention, in cludes" a'n'inductive network of the type illustrate'din- Figuref'connected in'parallel with a capacitiv'e network of the type illustrated inthe circuit of Figure; "It should be understoodthat any'other combination o f the Yinductive and ca 'pacitive reactance tube V circuits` described 'here'- in, or known in the art, may be employed.

Thelcominon output 'terminals 5, 5 ofthe inductive and capacitive reactance tube networks are respectively connectedv together, andthe network, components 'are proportioned. so that the effective net power factor of the'two Vnetworks .[5 is ;a .negative value1 to provide.: for; 'sustairnadl :oscillations in the.` combined :.circuit. A .typical .eX- amplexoi such combined-.inductive andcapacitive '.:reactance .tube networks, qrroportionedf `L to profvide :generated oscillationsv whichamayrbetadjust- -able zover'a; frequency range of: about; 200 to 2(1'00 cycles, includes a first reactance tube 2l having its: anode connected: to; thegoutputiterminal. 3 `and lto .onelterminal of arstnltlddll .resistor 23. Theremainingt terminaluofithe .first resistorZr; is Vconnected :through ean`.8i,00,0 api; iirst A'capacitor f2ztoigroun'd. .The. common terminals .ofi ther first resistor 2.3 'andfrrst capacitor 'T25 zare. connected `toszcne terminaloi' a .11ct secondi capacitor: 211 ,i .the

other terminal of whichyis connectedtthrougha 200,000JJ secondresistor :23'1- to lthe'rcontrolrzelectrode of the' first reactancetube :2L `z'lhe cathf ode ofV the4 rst reactance .tube .2l gis :coupled vto .ground and Ato the remaining "network routput terminalE through Aa iwf. bypasscapa'citor'l. Grid `bias l is applied .to 'the control electrode .ici the rstireaotancetubesZl .through la Zirrregohrn .grid resistor. .A 60.0? tutcapacitor glik connected between thev tube',controlelectrode4 andground completesfthephase.splitting'cir-cuit. y

:The second reactance tubeelllv has .its iianode electrode 'connected' to the'fnetwork: term-inala and vto* Oneterlninal :of.1ani:800..,auf. rthird Acapacitor 143. The-:remaining: terminal. oftheithird :capacitoi 43 is f connected tolonef terminal. of a..20,00.0 `third resistor 4r5,thef otherterminalpzoi' which. is connected tothe network output `terminali-5,.r and to ground. The common terminalsofthewthird capacitor Sand thirdresistcr drarenonnected through an V'800 cui. lfourth .capacitor =4^Tfto. .the control electrode of the --second 'reactance tube 4|. A 2 megohmv fourthi. resistor litisconne'cted between the Vcontrol Aelectrodepotthe' .second .reactance tube=12-l A.and thegroundedfnetworkzterminalv The Ycathode. of the second reactance tube `Il is'connectedto'th'e'cathode ofthe first .reactance-tube '21. Ascommon 160,000 .cathode resistor'! is connected between theacathodesrof the two tubes/land :thenegative terminal ofthe source of anode: potentiaLnot. shown. The-posi.- vtive .terminal ^of i the vanode energizing" voltage source is connectedgthrough afzlOOJlGW-,v anode .re- -silstcri53zto theanodesof tlreztwo reactance. .tubes y2 lll.

-When the .inductive reactanceY tubey network..

including therst react-ance .tube-tal, andthe capacitive reactance tube. network .including the second f reactance tube til are Ithus connected: in parallela phantom tuned circuit results ywhich comprises. the ei-ectivey inductive reactance of the inductive network and .the effective capacitive reactance of 'the .capacitive-network yforming 'a parallel resonant circuit. YIf `the net -eiective power vfactor of-the two'networlrs is anegative value, oscillations -will build up in `th'ephantom .circuit until .gridv current or lsatmation 'effects in one or` both of the: reactance tubes'rednces` the effective circuit-.power factor iso-zero. :Theoscillationswilly have/a frequency determined by the efiective parallel resonance of the phantom circuit.

.Biasing the control electrode of the inductive reactance tube more positivelyor biasing the control electrode of the capacitive reactance tube more negativelyboth with respect Lto the tube cathodes, increases the frequency, and vice versa. AElincef'fa..common cathode resistor-:5| is employed vi'or'looth tubes, a single controlling bias'volta'ge applied to the control electrode of the inductive reactance tube 2l effectively controls the effective ilO .of the inductive reactance tube.

the floadv 51.

Areactances.ofzthe two reactance .tubes :simultatofore are merelyl illustrative ci one' actual embodiment yof they invention for aparticular-frefluency range, and that any or kall values'may -be varied in .any manner known to'persons skilled inl the art.

.Since the fliest waveshape ortho-.generated `oscillations .occursat the control .electrode of -the: inductiverreactance tube, 1 and. since this lelec- Atrod'euis at'. relatively high impedance withzfrespect itofground, a-prefered connection toria load..device .el includes la :relatively srnall ycapacitor 5.9 'couzplingzthe control electrode of the firstereactance -tubeeE-l to the input vof 'a conventionaltbuffenamplierththe output yof Iwhich is 'connected )to It should be understoodwthatra-ny cther'type ci output coupling circuit knownd-n the art may be employed, .andl that outputpoten- 4timori-ray be derived from any other desiredpor- --tionvoi the oscillation; generating network.

The circuit of Figure 8 -isidentical-fto4 thefcircuit of 'Figure '7. theexceptionthatgpentode Vtherrnionic:tubes have been substitutedf-iorthe triode tubes sliow-ninfFigure 7. .All circuit connections. are "identical tothe circuit of `FigureV v'l :with: the exceptionv that: the. tubescreen electrodes connected to the corresponding tuberanodes through-screen resistorse E5 respectivelyfand 'the 'tube suppressor 'Y electrodes are connected directly-tothe respective-tube cathodes; 'The buiifer Y anilplier;V input. circuit is shownconnected tothermovable element 5?!y of asingle-pole,x doun .ble-throw switclrorwhich thexed contact-,sare

connected to the control electrode and'vscreen electrode, respectively,- of theerstreactance tube 52|. Actuation'oitheswitch contact 6.3.thereby permits selection of -generated potentials `from A'either the control. electrode'or screen-electrode of theV inductive `rear-:tance tube.

`lhusthe invent-ioni. described comprises arr irnproved ad-iustable frequency oscillation genera- .,tor v`employing :parallehconnected- .inductive and Acapacitive 'reactanoe .tube'circuits wherein the oscillationf frequency is controlled. by varying the .control electrode `bias et one or both. of thereactance tubes. -l Continuous .adjustmentof frequency. is therebyA provided overra. relatively .wide

. frequency: band.

.I lclaim my L invention: ':1. Anf oscillation;v generatory including, :inf-combination, a Aphantom :tuned network comprising a frequency determined. by the*effective` imped- .anccs of said f circuits.

2. oscillation generator..includingfin-.com-

bina-tion.. a 'first reacta-nce tube lcircuit;Y providing an eiiectively inductive output impedance, a second reactance tube circuit providing an effectively capacitive output impedance, means for energizing said circuits, and means connecting said circuits in mutually operable relation, Vthe net power factor of said connected circuits being a negative value to provide sustained oscillations therein at a frequency determined by the eifective impedances of said connected circuits.

` 3. Apparatus of .the type described in claim 2 including a source of adjustable potential, and means for applying said potential to at least one of said circuits to vary the effective impedance thereof and hence to control said oscillation frequency.

4. Apparatus of the type described in claim 2 including a source of adjustable potential, and means for applying said potential to at least one 'of said circuits to vary simultaneously in relatively opposite senses the impedances of said circuits for controlling said oscillation frequency.

5. An oscillation generator including, in combination, a rst reactance tube having at least a cathode, an anode and a control electrode, means for applying potentials relatively of the order of in phase quadrature relation to said anode and said control electrode, said control electrode potential being lagging, to provide an eectively inductive anode-cathode impedance, a second reactance tube having at least a cathode, a plate, and a control grid, means for applying potentials relatively of the order of in phase quadrature relation to said plate and said grid, said grid potential being leading, to provide an eifectively capacitive-plate-cathode impedance, and means connecting the anode-cathode circuit of said first tube to the plate-cathode circuit of said sec ond 'tube to provide a phantom tuned circuit characteristic of said effective impedances, the net power factor of said tuned circuit being a negative 'value to provide sustained oscillations therein at a frequency determined by the effective impedances of said connected circuits.

6. Apparatus of the type described in claim 5 including a source of adjustable potential, and means for applying said potential to at least one of said tubes to vary the eiiective impedance f thereof and hence to control said oscillation frequency.

'7. Apparatus of the type described in claim 5 including a common cathode resistor for said tubes, a source of adjustable bias potential, and means for applying said potential to bias one of said tubes to vary simultaneously in relatively opposite senses the effective impedances of said circuits for controlling said oscillation frequency.

8. An oscillation generator including, in coml bination, a first reactance tube having at least a cathode, an anode and a control electrode, means including a rst resistive-capacitive network connected to said first tube for applying potentials relatively of the order of in phase quadrature relation to said anode and said control electrode, said control electrode potential being lagging, to provide an elTectiVely inductive anode-cathode impedance, a, second reactance tube having at least a cathode, a plate, and a control grid, means including a second resistivecapacitive network connected to said second tube for applying potentials relatively of the order of in phase quadrature relation to said plate andl said grid, said grid potential being leading, to provide an eifectively capacitive plate-cathode impedance, and means connecting the anode-cathode circuit of said rst tube to the plate-cathode circuit of said secondl tube to .provide a phantom tuned circuit characteristic of said effective impedances, the net power factor of said tuned circuit being a negative value to provide sustained oscillations therein at a frequency determined by the effective impedances of said connected circuits.

9. An oscillation generator including, in` combination, a first reactance tube having at least a cathode, an anode and a control electrode, means including a first resistive-capacitive-inductive network connected to said first tube for applyg ing potentials relatively of the Vorder of in phase quadrature relation to said anode and said control electrode,- said control electrode potential being lagging, to provide an effectively inductive anode-cathode impedance, a second reactance tube having at least a cathode, a plate, and a control grid, means including a second resistivecapacitive-inductive network connected to said second tube for applying potentials relatively ofL the order of in phase quadrature relation to said plate and said grid, said gridV potential being leading, to provide an effectively capacitive platecathode impedance, and means connecting the anode-cathode circuit of said first tube to the plate-cathode circuit of saidsecond tube to procontrol electrode of said first tube for applying Y said generated oscillations to said load circuit.

:11. InV an oscillation generator, a first electron discharge device having an anode, a cathode, and a control grid, a phase shifting network coupling the anode of said device to the control grid of said device, the characteristic of the network being such as to relatively advance the phase of voltages of the operating frequency on the anodef of said device about V with respect to the phase f of the said voltages on the control grid, a second electron discharge device having a control grid, a cathode, and an anode, a second phase shifting network coupling the anode 'of the last mentioned device to its control grid,A the character of the last mentioned network being such as to relatively retard the phase of voltages of the said desired operating frequency on the anode of the last mentioned device about 90 with respect to the phase of the said voltages on the control grid of said last device, connections putting the anode to cathode impedances of said tubes in paralleLthe networks, the output impedances of the devices and the connections then having a net power factor which is negative, leads to the electrodes of said devices for applying thereto direct current operating potentials, and an output circuit coupled to at least one of said devices. VERNON D. LANDON.

REFERENCES YCITED The following referencesv are of record in the file of this patent:

UNITED STATES PATENTS 

